1. Field of the Invention
The invention concerns apparatus for supplying an oxygen containing gas to a fuel cell system, and fuel cell systems comprising such apparatus.
2. Description of the Related Art
Fuel cell systems with a gas generation system and at least one fuel cell, which for example can be a solid polymer (PEM) fuel cell, are known in the art. The gas generation system produces a hydrogen containing gas for the fuel cell from a is process stream, which contains carbon and hydrogen. Suitable process streams are hydrocarbons; such as for example natural gas or similar substances, or hydrocarbon derivatives such as alcohols, or higher hydrocarbons, such as benzene or similar substances. Liquid hydrocarbon derivatives such as methanol or ethanol, in particular are contemplated for use in motor vehicles, due to their high energy density and ease of transport.
The supply of the fuel cell system with an oxygen containing gas, typically air, is normally implemented by means of a compression device, e.g. a compressor, which supplies air to the cathode side of the fuel cell. Should the gas generation system also require an oxygen containing gas such as air, then this is typically supplied by means of a separate compressor in the gas generation system. The second compressor obtains its air either from the surroundings or draws in pre-compressed air from the air feed to the cathode side of the fuel cell. In general, the gas generation system requires air at least for selective oxidation devices, which oxidize residual carbon monoxide in the hydrogen containing gas to carbon dioxide, since carbon monoxide can damage the fuel cell catalyst material.
A system of this type is known from DE 197 55 116 C1, wherein the exhaust gases from the cathode chamber of the fuel cell (air and H2O) and from the anode area of the fuel cell (H2 and CO2) are fed to a catalytic burner.
The above mentioned design of apparatus to supply air to a fuel cell system has the disadvantage that it requires at least two compression devices. Each of the compression devices entails additional costs, weight, and volume, and creates noise, which are significant drawbacks in motor vehicle applications.
In addition, the air supply to the gas generation system is very complicated in such systems, since it requires a suitable regulation of the second compressor, as well as metering of the oxygen containing gas by means of complicated nozzles, such as Laval nozzles or similar devices.
Accordingly, there remains a need for apparatus for supplying an oxygen-containing gas to a fuel cell system, particularly apparatus embodying a simple, lightweight, and self regulating design. The present invention fulfils these needs and provides further related advantages.